Power assist mechanism for fluid control valves



Aug. 12, 1969 P. E. ROBINSON POWER ASSIST MECHANISM FOR FLUID CONTROL.VALVES Filed Aug. 24. 1967 States hit 3,460,438 POWER ASSIST MECHANISM FOR FLUID CONTROL VALVES Phillip E. Robinson, Wicklifie, Ohio, assignor to Parker- Hannifin Corporation, Cleveland, Ohio, a corporation of Ohio Filed Aug. 24, 1967, Ser. No. 663,037 Int. Cl. F15b 9/10, 13/042; Gd 11/00 U.S. Cl. 91376 12 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION This invention relates generally as indicated to a power assist mechanism for fluid control valves and more particularly to certain improvements in the manner of supplying fluid pressure to actuate the power assist mechanism.

It is common practice to provide a power boost for assisting the operator in the movement of large spool valves such as are used for controlling the operation of heavy load handling equipment and the like. However, the usual power assist mechanism is relatively complex and expensive, generally comprising a piston-cylinder assembly suitably connected to the spool valve and actuated by a four-way valve at the control rod for the mechanism. Other less expensive valves for actuating power assist mechanisms have been devised, but they usually provide a constant supply of fluid pressure to both ends of the power assist cylinder, whereby when one end of the cylinder is connected to exhaust to effect movement of the piston in that direction, there is substantial loss in actuating fluid.

SUMMARY OF THE INVENTION With the foregoing in mind, it is a principal object of this invention to provide a power assist mechansm for fluid control valves in which a relatively simple and inexpensive shuttle valve is used as the sole means for selectively supplying fluid pressure to one on both ends of the piston-cylinder assembly. A control rod is movable from a neutral position whereat the flow from both ends of the piston-cylinder assembly is blocked to one of two operating positions whereat one or the other end of the piston-cylinder assembly is connected to exhaust. With the control rod in an operative position, the shuttle valve automatically moves to a position closing flow to the exhausted end of the cylinder, whereby there is no fluid loss during stroking.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principle of the invention may be employed.

3,460,438 Patented Aug. 12, 1969 BRIEF DESCRIPTION OF THE DRAWING Referring now in detail to the drawing, FIG. 1 shows a preferred form of power assist mechanism generally in dicated at 1 bolted or otherwise secured to the housing 2 of a directional control valve 3 or the like having one or more spool valves 4 axially shiftable therein to control the operation of for example a double acting cylinder of heavy load handling equipment (not shown). The actuating end of the spool valve 4 may be received in a cavity 5 in the housing 6 of the power assist mechanism '1 for connection to the outer end 7 of a work rod 8 as by means of a tongue 9 extending from the work rod 8 into a bore 10 in the spool valve 4 where it is held in place by a pin 11. Apertures 12 in the side wall 13 permit free flow of air into and out of the cavity 5 for ease of movement of the associated end of the spool valve 4 therewithin.

The work rod 8 extends through the end wall 15 of the cavity 5 into the cylinder 16 of a piston-cylinder assembly 17 where it is suitably connected to the piston 18 for reciprocating movement therewith, the inner end 19 of the work rod 8 being enlarged and having an internally threaded recess 20 therein for threaded engagement with the axially projecting hub portion 21 of the piston 18. Suitable packings 22 contained in an internal groove 23 in the end wall 15 surrounding the work rod prevent loss of fluid (in this case air) from the cylinder 16 to the cavity 5.

For supplying air to opposite ends of the cylinder 16, there is provided a pair of axially spaced ports 25, 26 in the cylinder wall 27 in communication with an air inlet 28 via a stepped bore 29 in the cylinder wall 27. Contained within the bore 29 intermediate the ports 25, 26 is a shuttle valve 30 having tapered ends 31, 32 adapted selectively to be brought into sealing engagement with one or the other of valve seats 33, 34 mounted in the stepped bore 29 for blocking flow to one or the other of the ports 25, 26. The valve seat 33 may be press fit in the reduced end portion 35 of the stepped bore 29, whereas the seat 34 desirably has threaded engagement with the enlarged outer end portion 36 of the bore 29 to facilitate assembly of the valve seats 33, 34 and shuttle valve 30 within the bore 29.

Ordinarily the shuttle valve 30 is maintained in the mid position shown in FIG. 1 out of engagement with both valve seats 33, 34 by a pair of compression springs 40, 41 disposed in annular grooves 42, 43 in the shuttle valve 30 and contacting the adjacent valve seats, whereby full pressure is supplied to both sides of the piston 18 positively to maintain the piston in which ever position it happens to be within the cylinder 16. However, in the event that one or the other ends of the cylinder 16 is connected to exhaust in a manner to be subsequently fully explained, the shuttle valve 30 will be caused to move to a position blocking further flow to that end of the cylinder due to the pressure drop which occurs as the inlet air flows through the controlled clearance 44 between the wall of the bore 29 and one or the other of the outwardly directed flanges 45, 46 adjacent the ends of the shuttle valve toward the exhausting end of the cylinder. Accordingly, full pressure is made available for actuating the piston 18 in the direction of the exhausted cylinder end without any loss of air.

For selectively connecting one or the other ends of the cylinder 16 to exhaust, there is provided a control rod 47 extending outwardly from the piston 18 through a removable cylinder head 48. The inner end 49 of the control rod 47 is slidably received in a central opening 50 in the piston 18 which inner end 49 extends through the hub portion 21 into the recess 20 in the inner end 19 of the work rod 8. A snap ring 51 or the like precludes withdrawal of the control rod 47 from the piston 18 while permitting limited relative axial movement of the control rod 47 between the bottom 52 of the recess 20 and the adjacent end 53 of the piston 18. p

The control rod 47 has a plurality of axially spaced radial apertures 54, 55 adjacent its inner end 49 in communication with a central passage 56 in the control rod. When the inner end of the control rod is intermediate the recess bottom 52 and adjacent end 53 of the piston 18 as illustrated in FIG. 1, the outer ends of the apertures 54, 55 are blocked by a suitable packing 57 in the inner wall of the piston, whereby there is no loss of air from either end of the cylinder 16. However, axial inward movement of the control rod 47 will bring the inner radial apertures 54 into alignment with exhaust ports 58 in the piston 18 for exhausting the left end of the cylinder 16 as shown in FIG. 2, whereas axial outward movement of the control rod 47 will bring the outer radial apertures 55 into fluid communication with the right end of the cylinder 16 as in FIG. 3. With the radial apertures 54, 55 in communication with one or the other end of the cylinder 16, that end will be exhausted through the central passage 56 and radial ports 59 in the control rod 47 outwardly of the cylinder head 48. The central passage 56 may extend all the way through the inner end 49 of the control rod 47 to prevent air from being trapped in the recess 20.

A spring centering mechanism 60 may be provided for automatic return of the control 47 to the neutral position shown in FIG. 1. Such spring centering mechanism 60 may comprise a sleeve 61 having a pair of opposed spring followers 62, 63 contained therein with one of the spring followers 62 engaging an inturned flange 64 on the inner end of the sleeve 61 and a shoulder 65 on the control rod 47; and the other spring follower 63 similarly engaging an end plate 66 at the outer end of the sleeve 61 held in place by a snap ring 67, and a snap ring 68 on the control rod. Compressed between the followers 62, 63 is a spring 69, whereby when the control rod 47 is moved to the left as shown in FIG. 2, the right follower 63 moves therewith to compress the spring 69, and when the control rod 47 is moved to the right as in FIG. 3, the left follower 62 moves with the control rod to compress the spring. In each instance, when the control rod actuating force is released, the compressed spring 69 will cause a return movement of the control rod.

When the spool valve 4 is in the neutral position of FIG. 1 and no actuating force is applied to the control rod 47, the piston 18 of the power assist mechanism 1 will also be in neutral position with the radial apertures 54, 55 of the control rod 47 covered by the packing 57. The exact location of the radial apertures 54, 55 with respect to the piston 18 when in the neutral position may be adjusted by axial adjustment of the spring centering sleeve 61 which is in threaded engagement with the outer end of the cylinder head 48. Tightening of the lock nut 70 will prevent unintentional movement of the sleeve 61.

In any event, with the radial apertures 54, 55 blocked as aforesaid, the shuttle valve 30 will be in center position, FIG. 1, permitting high pressure air to enter both ends of the cylinder 16 for rigidly maintaining the piston 18 and spool valve 4 connected thereto in such neutral position.

Now, when it is desired to move the spool valve 4 to an operating position, the control rod 47 is moved in the desired direction as by actuation of a manually operated control lever (not shown) connected to the outer end of the control rod for exhausting one end of the cylinder 16 whereby the higher pressure in the other end of the cylinder acting on the piston 18 will cause the piston to move toward the exhausting end. At the same time, the pressure drop across one of the flanges 45, 46 of the shuttle valve 30 which occurs when an end of the cylinder 16 is connected to exhaust will cause the shuttle valve to move to a seated position precluding further flow of air into the exhausted end of the cylinder and consequently eliminating loss of air whereby full pressure air is supplied to the opposite end of the cylinder. Thus, for example, when the control rod 47 is moved toward the left as in FIG. 2, the radial apertures 54 communicate with the exhaust ports 58 for exhausting the left end of the cylinder 16, and the shuttle valve 30 is caused to be seated against the valve seat 33, whereby the higher pressure in the right end of the cylinder will cause the piston 18 and spool valve 4 connected thereto to move toward the left. Reverse movements take place when the control rod 47 is moved toward the right (see FIG. 3).

So long as the control rod 47 is being axially moved in one direction or the other and one end or the other of the cylinder 16 is connected to exhaust, the piston 18 will be pressure driven in that direction. However, as soon as the piston 18 has moved relative to the control rod 47 a distance sufficient to close oft the radial apertures 54, 55 by the packing 57, the shuttle valve 30 will be returned to the midposition of FIG. 1 for supplying full pressure to both sides of the piston 18 firmly to hold the piston 18 and spool valve 4 connected thereto in the desired selected position. Moreover, should there be a failure in the air supply, the spool valve 4 can still 'be manually actuated in either direction by the operator moving the control rod 47 in the desired direction to cause the inner end of the control rod or snap ring 51 carried thereby to engage the bottom wall 52 of the work rod 8 or adjacent end 53 of the piston 18 for movement of the piston 18 and spool valve 4 with the control rod.

From the above discussion, it can now be seen that the power assist mechanism of the present invention is of a simple and unique construction which facilitates actuation of a spool valve or the like simply by moving a control rod in the desired direction. A shuttle valve controls the flow of fluid pressure to the piston-cylinder assembly of the power assist mechanism in response to movements of the control rod. With the control rod in neutral position, full fluid pressure is supplied to both sides of the piston for firmly holding the spool valve in adjusted position, whereas when one or the other end of the piston-cylinder assembly is connected to exhaust, the shuttle valve automatically moves to a position blocking flow of fluid to the exhausting end of the assembly thereby permitting full flow to the other end for actuation without fluid loss.

Other modes of applying the principles of the invention may be employed, change being made as regards the details described provided the features stated in any of the following claims or the equivalent of such be employed.

I, therefore, particularly point out and distinctly claim as my invention:

1. A power assist mechanism comprising a housing containing a cylinder, a piston axially movable in said cylinder, a work rod projecting outwardly from said piston through one end of said cylinder for connection to a spool valve and the like, ports through which fluid pressure is supplied to both ends of said cylinder, means for selectively exhausting one or the other end of said cylinder, and a flow sensitive shuttle valve means movable from a midposition whereat full pressure is supplied to both ends of said cylinder through said ports to a position blocking flow of fluid to the port associated with whichever end of said cylinder is connected to exhaust whereby full pressure fluid is supplied to the cylinder end not connected to exhaust for actuation of said piston toward the exhausted end without loss of fluid.

2. The power assist mechanism of claim 1 wherein said flow sensitive shuttle valve means is spring biased toward such mid position and has outwardly directed flanges adjacent the ends thereof which provide for restricted flow to opposite ends of said cylinder, whereby when one or the other end of said cylinder is connected to exhaust, there is a pressure drop across the flange providing restrictive flow to the exhausted end of said cylinder which causes said shuttle valve means to move to said position blocking flow to said exhausted end of said cylinder as aforesaid.

3. The power assist mechanism of claim 2 wherein said shuttle valve means is disposed in a bore in said housing having opposite ends communicating with opposite ends of said cylinder through said ports, said bore containing a pair of axially spaced apart seats for engagement by opposite ends of said shuttle valve means to block the flow of fiuid entering said bore through an inlet intermediate said flanges to the exhausting end of said cylinder as aforesaid.

4. The power assist mechanism of claim 3 wherein there are annular grooves in opposite ends of said shuttle valve means, and spring means disposed in said annular grooves and contacting the adjacent valve seats for biasing said shuttle valve means toward such mid position.

5. The power assist mechanism of claim 1 wherein said means for selectively exhausting one or the other end of said cylinder comprises a control rod extending outwardly from said piston through the other end of said cylinder for connection to a control lever and the like, said control rod having radial apertures in the end adjacent said piston which communicate with a central exhaust passage in said control rod, said control rod being axially movable relative to said piston from a position whereat said radial apertures are blocked by said piston to positions whereat said radial apertures communicate with one or the other side of said cylinder for exhausting the same.

6. The power assist mechanism of claim 5 further comprising means for providing only limited relative axial movement of said control rod in opposite directions with respect to said piston, whereby should there be a loss of fluid pressure to both ends of said cylinder, said work rod may be manually actuated in either direction by continued movement of said control rod in the desired direction.

7. The power assist mechanism of claim 6 wherein said last-mentioned means comprises a recess in the inner end of said work rod into which the inner end of said control rod projects, and a snap ring on said inner end of said control rod for precluding withdrawal of said inner end of said control rod from said recess, said control rod being axially movable relative to said piston from a position whereat said inner end of said control rod is in engagement with the bottom of said recess to a position whereat said snap ring is in engagement with the adjacent end of said piston.

8. The power assist mechanism of claim 5 wherein there is a threaded connection between said work rod and piston and exhaust ports on that side of said piston into which said radial apertures in said control rod may be brought into alignment for exhausting that end of said cylinder.

9. The power assist mechanism of claim 5 further comprising a spring centering mechanism for said control rod, said spring centering mechanism being contained in a sleeve having threaded engagement with said housing to permit axial adjustment of said spring centering mechanism for adjusting the location of said radial apertures in said control rod when retained in place by said spring centering mechanism thus to adjust the neutral position of said piston in said cylinder.

10. A power assist mechanism comprising a housing containing a piston-cylinder assembly, ports at opposite ends of said cylinder, means for selectively exhausting one or the other end of said cylinder, a bore in said housing adjacent said cylinder communicating with said ports, an inlet passage in said housing intersecting said bore intermediate the ends thereof, a pair of axially spaced apart seats in said bore on opposite sides of said inlet passage, and shuttle valve means disposed in said bore intermediate said seats movable from a position in which fluid pressure entering said inlet passage is supplied to both ends of said cylinder through said bore and ports to a seated position blocking flow of fluid to whichever end of said cylinder is being exhausted in response to flow of fluid past said shuttle valve means into such exhausting cylinder end, whereby full pressure fluid is supplied to the end of said cylinder not exhausted to cause actuation of said piston toward the exhausted end without loss of fluid.

11. The power assist mechanism of claim 10 wherein said means for selectively exhausting one or the other end of said cylinder comprises a control rod extending outwardly from said piston through one end of said cylinder for actuation by a control lever and the like, said control rod having radial apertures in the end adjacent said piston which communicate with a central exhaust passage in said control rod, said control rod being axially movable relative to said piston from a position whereat said radial apertures are blocked by said piston to positions whereat said radial apertures communicate with one or the other side of said cylinder for exhausting the same.

12. The power assist mechanism of claim 11 further comprising a spring centering mechanism for said control rod, said spring centering mechanism being contained in a sleeve having threaded engagement with said housing to permit axial adjustment of said spring centering mechanism for adjusting the location of said radial apertures in said control rod when retained in place by said spring centering mechanism thus to adjust the neutral position of said piston in said cylinder.

References Cited UNITED STATES PATENTS 1,967,383 7/1934 Turgot 137118 2,926,635 3/1960 Leonard et al. 91378 2,992,633 7/1961 Stiglic et al. 91-376 3,017,750 1/1962 Kempson 91378 3,134,391 5/1964 Feibush 137-118 FOREIGN PATENTS 1,292,766 3/ 1962 France.

PAUL E. MASLOUSKY, Primary Examiner U.S. Cl. X.R. 

